.\" $NiH: zip_source_function.mdoc,v 1.6 2004/12/22 16:19:54 wiz Exp $
.\"
.\" zip_source_function.mdoc -- create data source from function
.\" Copyright (C) 2004 Dieter Baron and Thomas Klausner
.\"
.\" This file is part of libzip, a library to manipulate ZIP archives.
.\" The authors can be contacted at <nih@giga.or.at>
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.Dd December 22, 2004
.Dt ZIP_SOURCE_FUNCTION 3
.Os
.Sh NAME
.Nm zip_source_function
.Nd create data source from function
.Sh LIBRARY
libzip (-lzip)
.Sh SYNOPSIS
.In zip.h
.Ft int
.Fn zip_source_function "struct zip *archive" "zip_source_callback fn" "void *userdata"
.Sh DESCRIPTION
The function
.Fn zip_source_function
creates a zip source from the user-provided function
.Ar fn ,
which must be of the following type:
.Bd -literal
typedef ssize_t (*zip_source_callback)(void *state,
    void *data, size_t len, enum zip_source_cmd cmd);
.Ed
.Pp
When called by the library, the first argument is the
.Ar state
argument supplied to
.Fn zip_source_function .
The next two arguments are a buffer
.Ar data
of size
.Ar len
when data is expected to be returned, or else
.Dv NULL
and 0.
The last argument,
.Ar cmd ,
specifies which action the function should perform:
.Bl -tag -width XZIPXSOURCEXCLOSEXX -offset indent
.It Dv ZIP_SOURCE_OPEN
Prepare for reading.  Return 0 on success, \-1 on error.
.It Dv ZIP_SOURCE_READ
Read data into the buffer
.Ar data
of size
.Ar len .
Return the number of bytes placed into
.Ar data
on success, \-1 on error.
.It Dv ZIP_SOURCE_CLOSE
Reading is done.
.It Dv ZIP_SOURCE_STAT
Get meta information for the input data.
.Ar data
points to a struct zip_stat, which should be filled in.  Return 0 on
success, \-1 on error.
.It Dv ZIP_SOURCE_ERROR
Get error information.
.Ar data
points to an array of two ints, which should be filled with the libzip
error code and the corresponding system error code for the error that
occurred.  Return 0.
.\" XXX: we should document all error codes somewhere
.It Dv ZIP_SOURCE_FREE
Clean up and free all resources.  Return 0.
.El
.Pp
The library will always issue
.Dv ZIP_SOURCE_OPEN
before issuing
.Dv ZIP_SOURCE_READ .
When it no longer wishes to read from this source, it will issue
.Dv ZIP_SOURCE_CLOSE .
If the library wishes to read the data again, it will issue
.Dv ZIP_SOURCE_OPEN
a second time.  If the function is unable to provide
the data again, it should return \-1.
.Pp
.Dv ZIP_SOURCE_STAT
can be issued at any time.
.Dv ZIP_SOURCE_ERROR
will only be issued in response to the function
returning \-1.
.Dv ZIP_SOURCE_FREE
will be the last command issued.
.Sh RETURN VALUES
Upon successful completion, the created source is returned.
Otherwise,
.Dv NULL
is returned and the error code in
.Ar archive
is set to indicate the error.
.Sh ERRORS
.Fn zip_source_function
fails if:
.Bl -tag -width Er
.It Bq Er ZIP_ER_MEMORY
Required memory could not be allocated.
.El
.Sh SEE ALSO
.Xr zip_add 3 ,
.Xr zip_replace 3 ,
.Xr zip_source_buffer 3 ,
.Xr zip_source_file 3 ,
.Xr zip_source_filep 3 ,
.Xr zip_source_free 3 ,
.Xr zip_source_zip 3